The present invention relates to a drive shaft for a machine tool, for example a core drilling machine, able to be connected to a drilling tool, in particular a core bit, containing a cavity which substantially extends over the entire length of the drive shaft and along the rotational axis, wherein the cavity contains at least one inflow opening, wherein through the opening water can be fed along the drive shaft into the drilling tool.
A water supply system is an essential and indispensable necessity in almost all core drilling work as well as in numerous other works with large and powerful machine tools (such as, for example, saws, angle grinders or the like). Especially when using a core drill for drilling holes in mineral rock with a core bit rotationally offset from the core drill, flushing the drill bit is absolutely necessary. Through the water used for flushing the rock detached during core drilling and the resulting dust are washed out of the drill bit and from the borehole in the form of drilling mud. Without this flushing of the drilling mud, the drill bit would run hot in a very short time and thus set itself firmly in the well in a such a manner that further drilling is no longer possible.
A water supply system for use with a machine tool, such as a core drilling machine, according to the prior art is disclosed, for example, in the German patent application DE 10 2006 035 345 A1.
The core drills used in core drilling are often extremely powerful and accordingly have a high energy consumption. Moreover, the development of heat during the execution of core drilling work presents a considerable problem in core drilling. An excessive heat buildup inside a core drill can significantly reduce its performance and thus the efficiency of a core drill. Further, permanent damage to the entire core drill or individual components is also possible. In addition, there is also the risk that a user of the core drill can be injured by an excessively heated outer wall, which is caused by the heat generated inside the core drill.
It is therefore the object of the present invention to solve the problems described above, and in particular to provide a drive shaft for a machine tool, such as a core drill connectable with a drilling tool, in particular a drill bit, with which damage to the machine tool and heat-related injury to the user can be avoided effectively.
The present invention relates to a drive shaft for a machine tool, for example a core drilling machine, able to be connected to a drilling tool, in particular a core bit, containing a cavity which substantially extends over the entire length of the drive shaft and along the rotational axis, wherein the cavity contains at least one inflow opening, through which water can be fed along the drive shaft into the drilling tool.
The drive shaft is characterized according to the invention in that an insertion device is provided in the cavity, through which the water is then guided to cool the drive shaft first in a first direction and then in a second direction, wherein the water has direct contact with the inside of the cavity at least in the first direction. In this way, the water which is actually intended for flushing the drill bit is efficiently used for cooling the drive shaft and hence for cooling the core drill. By guiding the water into a first and a second direction, the water is passed through the cavity of the drive shaft longer, whereby higher heat absorption may be generated by the water and thus better cooling.
According to an advantageous embodiment of the present invention, it may be possible that the insertion device comprises a guide element, which contains at least a first surface for guiding the water in the first direction and a second surface for guiding the water in the second direction. By using a first and second surface on the guide element, a large contact area with the inner wall of the cavity and, consequently, the largest possible removal of heat, is generated.
In order to generate the largest possible volumetric flow rate for absorbing heat energy, it may be advantageous that the guide element is configured spirally along the cavity.
According to a further advantageous embodiment, it may be possible that the guide element is configured as a planar flat profile. Thus a low-cost and easy-to-manufacture guide member can be provided in a simple manner.
To produce a largest possible volume flow in the second direction, it may be useful for the guide element to be configured as a bent flat profile, wherein the first surface is convex and the second surface has a concave shape.
In order to produce the largest possible volume flow of the water in the first direction and so as to maximize heat absorption by the water, it may be advantageous for the guide element to include a longitudinal fold, wherein the first surface is positioned along the outer side of the longitudinal fold and the second surface is positioned along the inner of the longitudinal fold.
According to a further advantageous embodiment of the present invention, it may be advantageous that the guide element is configured as a tube, wherein the first surface is realized through the outer wall of the tube and the second surface by the inner wall of the tube. This allows the greatest possible flow of water in the first direction and so as to maximize the heat absorption generated by the water.
According to a further advantageous embodiment, it may be possible that at least one radially extending longitudinal rib is positioned on the outer wall of the tube. This water is guided as straight as possible in the first direction and stabilizes the guide element in the cavity.
In order to avoid an adverse twisting or slipping of the insertion device in the cavity, it may be expedient according to a further embodiment, that at the insertion device at least one holding device is provided which is engageable in a corresponding fixing element on the cavity and whereby a relative motion between the insertion device and the drive shaft is prevented.
Furthermore, it may be possible that the holding device is configured as a spring element. This enables the insertion device to equalize vibrations and shocks in the cavity, without it being changed from its envisaged position in the cavity.
Further advantages arise from the following description of the figures. In the figures, various embodiments of the present invention are shown. The figures, the description and the claims contain numerous features in combination. The expert will expediently also consider the features individually and combine them to form further reasonable combinations.